This invention relates to organo-soluble cellulose ethers, and in particular to hydroxyalkoxyl substituted ethylcellulose ethers.
Common commercially available cellulose ethers such as methylcellulose, hydroxyethyl methylcellulose, hydroxypropyl methylcellulose, hydroxypropylcellulose and the like are employed as thickeners, protective colloids, film formers and for other uses in aqueous systems. While these cellulose ethers are useful in aqueous systems, the water-soluble ethers are generally insoluble in organic solvents and nonthermoplastics. Accordingly, these cellulose ethers cannot be employed in organic systems. For example, it is difficult to employ such cellulose ethers as additives in organic solvent systems, such as inks and the like.
To meet the need for a cellulose ether with organic solubility, more hydrophobic cellulose derivatives have been developed. Such compositions include ethylcellulose, ethylhydroxypropyl methylcellulose and ethylhydroxyethylcellulose have been developed. While these cellulose ethers are both organo-soluble and thermoplastic, they have other deficiencies which significantly limit their utility. For example, most ethylcellulose ethers are insoluble in nonpolar organic solvents, such as the hydrocarbons and their halo, nitro, and cyano substituted derivatives which have low solubility parameters. Generally, if solubility in such nonpolar solvents is required, the ethylcellulose must be substantially completely substituted, i.e., have an ethoxyl degree of substitution of about 3. Unfortunately, ethylcellulose with a degree of substitution greater than about 2.5 exhibits a tendency to crystallize, which renders the cellulose ether insoluble in most solvents.
Still another disadvantage of known technology involves the fact that the preparations of ethylhydroxyethylcellulose and ethylhydroxypropyl methylcellulose are not particularly efficient nor effective. The ethylene oxide commonly used in the preparation of ethylhydroxyethylcellulose can react with water, ethyl chloride and other reagents present in the reaction mixture. Consequently, the overall yield of the process is greatly reduced and a variety of by-products are formed which are difficult to remove from the product.
Accordingly, a cellulose ether which is soluble in nonpolar organic solvents and is efficiently and effectively prepared would be highly desirable.